The Melbourne researcher who made the discovery says cosmetic surgeons should screen for the disorder and refuse to carry out procedures on sufferers because they will not see any improvement.

''About 14 per cent of people getting plastic surgery have been diagnosed with BDD,'' said Ben Buchanan, who conducted the research as a PhD candidate at Monash University. ''Yet it's known they will be left wholly dissatisfied with the surgery. They shouldn't be getting it in the first place.''

Dr Buchanan's finding was published in the journal Psychological Medicine this month.

He said the disorder was five times more prevalent than anorexia, caused higher levels of psychological impairment and the true number of sufferers seeking ''unnecessary surgery'' was not known. Research into the condition was hampered by sufferers' shyness.

Advertisement

''They don't want to talk to anyone about their feelings,'' he said. ''They see themselves as unbearably ugly or disfigured and they're too embarrassed to talk about it.''

Dr Buchanan's research, the biggest neuroimaging study of body dysmorphic disorder in the world, involved 40 patients referred by specialists. Using an MRI machine and a new neuroimaging technique called diffusion tensor imaging, Dr Buchanan found there was a weak connection between the amygdala, the brain's emotion centre, and the orbitofrontal cortex, the rational part of the brain that helps regulate and calm down emotional arousal.

''When BDD sufferers become emotionally distressed about their looks, they find it very difficult to wind down because the emotional and rational parts of their brain aren't communicating effectively,'' he said.

Where previous neuroimaging showed only parts of the brain lit up by activity, diffusion tensor imaging tracks and evaluates how different parts of the brain talk to one another.

''The imaging can measure the strength of the nerve fibres between the different areas,'' Dr Buchanan said. ''If the connection is weak, information is not getting through or is composed in some way that is deficient.''

Dr Buchanan said BDD sufferers had significant problems with social functions or going to work.

He said the false beliefs were so strong they would be ''highly resistant'' to a surgeon saying no to their demands for a procedure.

''This should be a red flag to surgeons that a patient, in fact, suffers BDD,'' he said.

Dr Buchanan's research also found cognitive behaviour therapy may be the most effective mechanism to reduce BDD symptoms.

The Australian Society of Plastic Surgeons did not respond to questions from Fairfax Media.